1. Field of the Invention
The present invention relates to a camera and a camera zoom control method, and in particular to a camera and a camera zoom control method where plural lenses that image a subject image are disposed at respectively different positions and which can conduct stereo photographing using the plural lenses.
2. Description of the Related Art
In recent years, digital cameras, such as digital still cameras and digital video cameras, provided with both an optical zoom function and an electronic zoom function have become more common.
Conventionally, in digital cameras of this type, from the standpoint of maintaining the quality of images (subject images) obtained by photographing, zooming in the range of the corresponding zoom magnifying power with the optical zoom function has been conducted with the optical zoom function, and zooming resulting from the electronic zoom function has been conducted only when conducting zooming exceeding this range. The electronic zoom function is also called a digital zoom function, but in the present specification both will be collectively referred to as an “electronic zoom function”.
When zooming is conducted with the optical zoom function, it is necessary to move the lens disposed in the digital camera to change the focal length resulting from the lens. A motor (called a “zoom motor” below) such as a stepping motor is usually used as moving means for this purpose (e.g., see Japanese Patent Application Laid-Open Publication (JP-A) Nos. 2000-224455 and 2001-211373).
Thus, in digital cameras of this type, the zoom motor is driven when zooming is conducted in the range of the corresponding zoom magnifying with the optical zoom function. Therefore, there has been the problem that the power consumption is large.
In this manner, when the power consumption at the time of zooming is large, in a digital camera using a battery as the power source assuming use in a mobile environment, the problem arises that the number of photographing images is reduced due to the affect of the power consumed by the zoom motor. In a digital camera that can execute various kinds of internal processing in a multitask manner with the purpose of speeding up the photographing speed, the problem arises that sometimes a limit must be imposed, due to the affect of the power consumed by the zoom motor, on the internal processing that can be executed in parallel.
Thus, in order to solve the problem that the power consumption at the time of zooming is large, JP-A No. 2000-111785 proposes technology where a subject image, to which electronic zoom processing has been carried out in accordance with the focal length set by a zoom button without moving the zoom mechanism of the lens, is displayed on a monitor at the point in time prior to photographing, and at the time of photographing, the lens is set by the zoom mechanism to the set focal distance, whereby the power consumption by the zoom mechanism at the time of zooming is reduced.
In recent years, interest with respect to three-dimensional stereo images has risen, and cameras that can conduct stereo photographing (here, called “stereo cameras”) are also being manufactured.
Stereo cameras of this type are usually provided with plural imaging systems for photographing a subject and configured to record, as image information representing a stereo image, information of plural images obtained by conducting photographing with each imaging system at the same time from different positions. Additionally, when conducting zooming in such a stereo camera, the zoom magnifying powers of the imaging systems are set to the same zoom magnifying power corresponding to the zoom operation by the user.
Thus, by applying the technology of JP-A No. 2000-111785 to a stereo camera of this type, conducting electronic zoom processing in regard to each imaging system prior to photographing and setting the optical zoom at the time of photographing, the power consumed by the zoom mechanism of each imaging system at the time of photographing can be reduced.
However, when the technology of JP-A No. 2000-111785 is applied to a conventional stereo camera, the power consumed at the time of zooming can be reduced but the zoom mechanisms are moved only at the time of photographing. Thus, there is no problem when the difference between the zoom magnifying power set by electronic zoom processing prior to photographing and the zoom magnifying power of the optical zoom set at the point in time of photographing is small, but when this difference is large, such as when the zoom magnifying power set by electronic zoom processing is the minimum zoom magnifying power and the zoom magnifying power of the optical zoom set at the time of photographing is the maximum zoom magnifying power, there is the problem that the time difference between the timing of the photographing instruction resulting from depressing the release button (the shutter) and the timing of the actual photographing becomes large. When this time difference is large, not only does the feeling of operation at the time of photographing become uncomfortable for the user, but sometimes the precious opportunity to capture the subject at just the right time is missed, and this problem is serious.